Fix bhyvectl so it works correctly on AMD/SVM hosts. Also, add command line
options to display some key VMCB fields.

The set of valid options that can be passed to bhyvectl now depends on the
processor type. AMD-specific options are identified by a "--vmcb" or "--avic"
in the option name. Intel-specific options are identified by a "--vmcs" in
the option name.

Submitted by: Anish Gupta (akgupt3@gmail.com)